It was Nimoy who asserted that Roddenberry leaked the Enterprise news.

He didn't leak it very well. I'm sure I recall the first we knew of it was "Starlog" mentioning reaction to the trailer.

My Name Is Legion wrote:

Bennett and company certainly did resent Roddenberry's tendency to leak information about the later Trek movies - same thing happened with Spock's death in TWOK.

There was an interesting "Starlog" interview with Bennett, many years after the fact, where he actually thanks Susan Sackett for that leak, since to patch up the problem of the surprise being blown, they came up with the Kobayshi Maru scenario, in which it appears that Spock - and McCoy, Uhura and Sulu - all seemingly die, and we realise it is a purposely poorly-acted ruse. Only to have Spock die for real towards the end of the film.